U.S. patent application number 10/432930 was filed with the patent office on 2004-04-08 for water-developable photosensitive resin for flexography.
Invention is credited to Araki, Yoshifumi, Kobayashi, Hiromi.
Application Number | 20040067442 10/432930 |
Document ID | / |
Family ID | 26604727 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040067442 |
Kind Code |
A1 |
Araki, Yoshifumi ; et
al. |
April 8, 2004 |
Water-developable photosensitive resin for flexography
Abstract
An object of the present invention is to provide a
photosensitive resin composition which is excellent in the
compatibility (dispersibility) of photosensitive resin composition
components, developability with aqueous developer solution, water
resistance, image reproducibility, print wear characteristics in
printing with a water base ink and plate wiping-off resistance in
removal of ink adhered to any printing plate. The present invention
relates to a photosensitive resin composition comprising a
hydrophilic copolymer (A) obtained by copolymerizing at least (1) 2
to 15 parts by mass of an unsaturated monomer having a carboxyl
group, (2) 50 to 80 parts by mass of a conjugated diene-type
monomer, (3) 3 to 20 parts by mass of an aromatic vinyl compound,
and (4) 3 to 30 parts by mass of an alkyl (meth)acrylate.
Inventors: |
Araki, Yoshifumi; (Fuji,
JP) ; Kobayashi, Hiromi; (Yokohama, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
26604727 |
Appl. No.: |
10/432930 |
Filed: |
May 28, 2003 |
PCT Filed: |
November 27, 2001 |
PCT NO: |
PCT/JP01/10336 |
Current U.S.
Class: |
430/300 |
Current CPC
Class: |
G03F 7/033 20130101;
Y10S 430/111 20130101 |
Class at
Publication: |
430/300 |
International
Class: |
G03F 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2000 |
JP |
2000-361371 |
Apr 10, 2001 |
JP |
2001-111193 |
Claims
1. A photosensitive resin composition for flexographic printing
comprising: (A) a hydrophilic copolymer, (B) a thermoplastic
elastomer, (C) a photopolymerizable unsaturated monomer, and (D) a
photopolymerization initiator, wherein the hydrophilic copolymer
(A) is a polymer obtained by copolymerizing at least: (1) 2 to 15
parts by mass of an unsaturated monomer having a carboxyl group,
(2) 50 to 80 parts by mass of a conjugated diene-type monomer, (3)
3 to 20 parts by mass of an aromatic vinyl compound, and (4) 3 to
30 parts by mass of an alkyl (meth)acrylate, per 100 parts by mass
of unsaturated monomers for use in the copolymerization.
2. The photosensitive resin composition for flexographic printing
according to claim 1, wherein the hydrophilic copolymer (A) has a
gel ratio, as measured with toluene, of 80 to 95%.
3. The photosensitive resin composition for flexographic printing
according to claim 1 or 2, wherein the hydrophilic copolymer (A) is
one synthesized by emulsion polymerization and the polymerization
temperature is 60.degree. C. or higher.
4. The photosensitive resin composition for flexographic printing
according to claim 3, wherein the polymerization temperature is
70.degree. C. or higher.
5. The photosensitive resin composition for flexographic printing
according to any one of claims 1 to 4, wherein the hydrophilic
copolymer (A) is a polymer obtained by copolymerizing at least: (1)
2 to 15 parts by mass of the unsaturated monomer having a carboxyl
group, (2) 50 to 80 parts by mass of the conjugated diene-type
monomer, (3) 3 to 20 parts by mass of the aromatic vinyl compound,
and (4) 3 to 30 parts by mass of the alkyl (meth)acrylate, and
further 0.5 part by mass or less of a polyfunctional vinyl
compound, per 100 parts by mass of unsaturated monomers for use in
the copolymerization.
6. The photosensitive resin composition for flexographic printing
according to claim 1, wherein the hydrophilic copolymer (A) has a
number average particle diameter ranging from 5 to 100 nm.
7. The photosensitive resin composition for flexographic printing
according to any one of claims 1 to 6, wherein an emulsifier used
in emulsion copolymerization of the hydrophilic copolymer (A)
comprises a nonreactive emulsifier in an amount of less than 1 part
by mass and an reactive emulsifier in an amount of 1 to 20 parts by
mass, per 100 parts by mass of the hydrophilic copolymer.
8. The photosensitive resin composition for flexographic printing
according to claim 7, wherein the reactive emulsifier contains a
polyoxyalkylene structure.
9. A photosensitive structure for flexographic printing, comprising
a laminate structure comprising a support and a layer of the
photosensitive resin composition according to any one of claims 1
to 8 formed on a surface of the support.
Description
TECHNICAL FIELD
[0001] The present invention relates to a photosensitive resin
composition for printing plates which can be developed with an
aqueous developer solution.
BACKGROUND ART
[0002] Common photosensitive resin printing plates which can be
processed by an aqueous developer solution generally consist of a
structure comprising: a support layer for maintaining dimensional
precision; a layer of photosensitive resin composition comprising a
mixture of a hydrophilic copolymer, a hydrophobic resin such as a
thermoplastic elastomer, a photopolymerizable unsaturated monomer,
a photopolymerization initiator, etc. on the support layer; and
further thereon a thin flexible film layer, known as a slip layer
or a protective layer, and a thin layer which can be ablated by an
infrared laser.
[0003] With respect to a method of producing a printing plate from
the above structure, a relief for printing is formed, when a
flexible film layer is provided, by sticking a negative film
thereonto, irradiating the structure with active rays through the
negative film so as to selectively photo-cure specific areas of the
photosensitive resin composition layer whereby an image is formed,
and thereafter removing unexposed areas of the photosensitive resin
composition layer with an aqueous developer solution
(development).
[0004] With respect to such a photosensitive resin composition for
flexographic printing, it is preferred from the viewpoint of
faithfully obtaining needed images that individual components in
the composition are finely and uniformly dispersed. Further, for
shortening the time required for preparing a printing plate, it is
preferred to increase the rate of development of the photosensitive
resin composition. The photosensitive resin composition has to have
satisfactory developability in an aqueous developer solution as
above, but also, when made into a printing plate, high print wear
characteristics of printing plate when used with an aqueous ink and
also rupture resistance of the printing plate when the ink adhering
to the printing plate after printing is wiped off with water or the
like (plate wiping-off resistance). That is, the printing plate is
required to have high water resistance and a high plate wiping-off
resistance.
[0005] Various photosensitive resins which can be developed in an
aqueous developer solution have been proposed in conformity with
intended uses. JP-A-7-114180 proposes a photosensitive resin
composition comprising a hydrophilic copolymer wherein phosphoric
ester groups are contained as an essential component. An object of
the invention described therein is to provide a resin composition
which can be processed in an aqueous developer solution, which has
photosensitivity, transparency and workability, and which can be
cured into a cured product with excellent transparency and
low-temperature elasticity. However, because of the use of
phosphoric ester groups as an essential component of hydrophilic
groups of the hydrophilic copolymer, its water resistance, plate
wiping-off resistance and print wear characteristics of the
printing plate from the resin composition are not necessarily
satisfactory. In Comparative Example 2C of the laid-open reference,
methacrylic acid is used in place of the phosphoric ester. However,
the amount of methacrylic acid used is so large that its water
resistance and print wear characteristics of the printing plate
from the resin composition are not satisfactory.
[0006] U.S. Pat. No. 5,731,129 proposes a photosensitive resin
composition comprising a hydrophilic copolymer wherein an
unsaturated monomer having a carboxyl group and a conjugated diene
monomer are contained as essential components while an aromatic
vinyl compound and an alkyl (meth)acrylate are contained as
optional components. An object of this invention is to suppress the
swelling, strength drop and dimensional change by water, at the
time of developing in an aqueous developer solution. However,
because all of an unsaturated monomer having a carboxyl group, a
conjugated diene monomer, an aromatic vinyl compound and an alkyl
(meth)acrylate are not simultaneously employed in the monomers for
the polymerization of the hydrophilic copolymer, the compatibility
of the resin composition, developability with an aqueous developer
solution and the print wear characteristics of printing resultant
plates are not necessarily satisfactory.
[0007] JP-A-63-8648 proposes a photosensitive resin composition
comprising hydrophilic copolymer particles crosslinked by a
polyfunctional vinyl compound. An object of this invention is to
suppress deteriorations of curing efficiency and relief image
reproducibility by light, by using a hydrophobic resin as a matrix
component and hydrophilic resin particles that have chemically and
optically approximate compositions to each other. However, because
a conjugated diene is not used as a monomer in the polymerization
of the hydrophilic copolymer, the water resistance and print wear
characteristics of the printing plate are not satisfactory.
Further, because of the use of a polyvinyl compound in high
proportion, satisfactory print wear characteristics cannot be
attained.
[0008] JP-B-5-5106 proposes a photosensitive resin composition
comprising a hydrophilic polymeric compound having carboxyl groups.
An object of this invention is to suppress a decrease in resistance
to a water or an alcohol base ink by using the above hydrophilic
polymeric compound and a hydrophobic copolymer as a polymer
component. However, because all of an unsaturated monomer having a
carboxyl group, a conjugated diene-type monomer, an aromatic vinyl
compound and an alkyl (meth)acrylate are not simultaneously
employed in the monomers for use in the polymerization of the
hydrophilic copolymer, the compatibility and developability with
aqueous developer solution of resin composition and the print wear
characteristics of resultant printing plates are not necessarily
satisfactory.
[0009] U.S. Pat. No. 5,348,844 proposes a photosensitive resin
composition comprising a hydrophilic copolymer wherein an
unsaturated monomer having a carboxyl group, a conjugated
diene-type monomer and a polyfunctional vinyl compound are
contained as the essential components while an aromatic vinyl
compound and an alkyl (meth)acrylate are contained as optional
components. An object of this invention is to suppress
deteriorations of elasticity, print wear characteristics and relief
image reproducibility. However, because all of an unsaturated
monomer having a carboxyl group, a conjugated diene-type monomer,
an aromatic vinyl compound and an alkyl (meth)acrylate are not
simultaneously employed, the compatibility and developability with
aqueous developer solution of resin composition and the print wear
characteristics of resultant printing plates are not necessarily
satisfactory.
[0010] JP-A-2001-512180 proposes a photosensitive resin composition
comprising a hydrophilic copolymer from ethylenically unsaturated
monomers including a surfactant monomer. It is described therein
that a hydrophilic polymer can be produced without employing a
hydrophilic monomer as an essential raw material and by a one-stage
polymerization process. However, because all of an unsaturated
monomer having a carboxyl group, a conjugated diene monomer, an
aromatic vinyl compound and an alkyl (meth)acrylate are not
simultaneously employed in the monomers for use in the production
of the hydrophilic copolymer, the water resistance and print wear
characteristics of the printing plate from the resin composition
are not necessarily satisfactory.
[0011] As apparent from the above, the conventional photosensitive
resin compositions which can be developed with an aqueous developer
solution, because of being mixtures of a hydrophilic component and
a hydrophobic component as mentioned above, have posed such
problems that the mutual compatibility (dispersibility) thereof is
questionable, that the developability with aqueous developer
solution of resin composition is low, that the printing plate
prepared therefrom through exposure exhibits low print wear
characteristics, low water resistance or low plate wiping-off
resistance.
[0012] The technological problem to be solved in the present
invention is, with a view toward solving the above problems, to
provide a photosensitive resin composition which can simultaneously
satisfy the following six requirements:
[0013] 1) the mutual compatibility (dispersibility) of components
in the photosensitive resin is high;
[0014] 2) the developing time with an aqueous developer solution is
short;
[0015] 3) the image reproducibility of printing plate is high;
[0016] 4) the water resistance of the printing plate is high;
[0017] 5) the wear resistance (abrasion resistance) of the printing
plate (especially upon using a water base ink) is high; and
[0018] 6) the plate wiping-off resistance exhibited upon removing
of the ink adhering to the printing plate is high.
SUMMARY OF THE INVENTION
[0019] The inventors have found that the above problem can be
solved by the use of a hydrophilic polymer obtained by
simultaneously employing at least (1) an unsaturated monomer having
a carboxyl group, (2) a conjugated diene-type monomer, (3) an
aromatic vinyl compound and (4) an alkyl (meth)acrylate at certain
ratios. The present invention has been completed on the basis of
this finding.
[0020] The first aspect of the present invention relates to a
photosensitive resin composition for flexographic printing
comprising:
[0021] (A) a hydrophilic copolymer,
[0022] (B) a thermoplastic elastomer,
[0023] (C) a photopolymerizable unsaturated monomer, and
[0024] (D) a photopolymerization initiator, wherein the hydrophilic
copolymer (A) is a polymer obtained by copolymerizing at least:
[0025] (1) 2 to 15 parts by mass of an unsaturated monomer having a
carboxyl group,
[0026] (2) 50 to 80 parts by mass of a conjugated diene-type
monomer,
[0027] (3) 3 to 20 parts by mass of an aromatic vinyl compound,
and
[0028] (4) 3 to 30 parts by mass of an alkyl (meth)acrylate, per
100 parts by mass of unsaturated monomers for use in the
copolymerization.
[0029] The second aspect of the present invention relates to the
photosensitive resin composition for flexographic printing
according to the above first aspect of the present invention,
wherein the hydrophilic copolymer (A) has a gel ratio, as measured
with toluene, of 80 to 95%.
[0030] The third aspect of the present invention relates to the
photosensitive resin composition for flexographic printing
according to the above first or second aspect of the present
invention, wherein the hydrophilic copolymer (A) is one synthesized
by emulsion polymerization and the polymerization temperture is
60.degree. C. or higher.
[0031] The fourth aspect of the present invention relates to the
photosensitive resin composition for flexographic printing
according to the above third aspect of the present invention,
wherein the polymerization temperature is 70.degree. C. or
higher.
[0032] The fifth aspect of the present invention relates to the
photosensitive resin composition for flexographic printing
according to any one of the above first to fourth aspects of the
present invention, wherein the hydrophilic copolymer (A) is a
polymer obtained by copolymerizing at least:
[0033] (1) 2 to 15 parts by mass of the unsaturated monomer having
a carboxyl group,
[0034] (2) 50 to 80 parts by mass of the conjugated diene-type
monomer,
[0035] (3) 2 to 30 parts by mass of the aromatic vinyl compound,
and
[0036] (4) 3 to 30 parts by mass of the alkyl (meth)acrylate, and
further 0.5 part by mass or less of a polyfunctional vinyl
compound, per 100 parts by mass of unsaturated monomers for use in
the copolymerization.
[0037] The sixth aspect of the present invention relates to the
photosensitive resin composition for flexographic according to the
above first aspect of the present invention, wherein the
hydrophilic copolymer (A) has a number average particle diameter
ranging from 5 to 100 nm.
[0038] The seventh aspect of the present invention relates to the
photosensitive resin composition for flexographic printing
according to any one of the above first to sixth aspects of the
present invention, wherein an emulsifier used in emulsion
copolymerization of the hydrophilic copolymer (A) comprises a
nonreactive emulsifier in an amount of less than 1 part by mass and
a reactive emulsifier in an amount of 1 to 20 parts by mass, per
100 parts by mass of the hydrophilic copolymer.
[0039] The eighth aspect of the present invention relates to the
photosensitive resin composition for flexographic printing
according to the above seventh aspect of the present invention,
wherein the reactive emulsifier contains a polyoxyalkylene
structure.
[0040] The ninth aspect of the present invention relates to a
photosensitive structure for flexographic printing, comprising a
laminate structure comprising a support and a layer of the
photosensitive resin composition according to any one of the above
first to eighth aspects of the present invention formed on a
surface of the support.
BRIEF DESCRIPTION OF THE DRAWING
[0041] FIG. 1 is a view diagrammatically showing a test performed
for evaluation of a printing plate wiping-off resistance.
BEST MODE FOR CARRYING OUT THE INVENTION
[0042] The present invention will be described in detail
hereinbelow.
[0043] As the unsaturated monomers having a carboxyl group (1),
which is an essential component of the hydrophilic copolymer (A),
for example, a monobasic acid monomer having a carboxyl group and a
dibasic acid monomer having a carboxyl group are included.
[0044] More specifically, the monobasic acid monomer can be, for
example, any of acrylic acid, methacrylic acid, crotonic acid,
vinylbenzoic acid and cinnamic acid, as well as the sodium,
potassium or ammonium salts thereof.
[0045] The dibasic acid monomer can be, for example, any of
itaconic acid, fumaric acid, maleic acid, citraconic acid and
muconic acid, as well as the sodium, potassium or ammonium salts
thereof.
[0046] In the present invention, one or more unsaturated monomers
having a carboxyl group can be used.
[0047] Among these, from the viewpoint of availability, the
monobasic acid monomer is preferably acrylic acid or methacrylic
acid, and the dibasic acid monomer is preferably itaconic acid or
fumaric acid.
[0048] The unsaturated monomer having a carboxyl group (1) is used
in an amount of 2 to 15 parts by mass per 100 parts by mass of
unsaturated monomers for use in the polymerization of hydrophilic
copolymer (A). When the amount is smaller than 15 parts by mass,
excellent water resistance and workability can be attained. When
the amount is larger than 2 parts by mass, satisfactory
developability with aqueous developer solution can be attained. The
amount is more preferably in the range of 2 to 10 parts by
mass.
[0049] As the conjugated diene-type monomer (2), which is an
essential component of the hydrophilic copolymer (A), for example,
1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene,
2-ethyl-1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene,
chloroprene, 2-chloro-1,3-butadiene or cyclopentadiene are
included.
[0050] In the present invention one or more conjugated diene
monomers can be used.
[0051] Among these, from the viewpoint of availability, butadiene
is preferred.
[0052] The conjugated diene (2) is used in an amount of 50 to 80
parts by mass per 100 parts by mass of unsaturated monomers for use
in the polymerization of the hydrophilic copolymer (A). When the
amount is smaller than 80 parts by mass, excellent processability
can be attained. When the amount is larger than 50 parts by mass,
deteriorations of water resistance and print wear characteristics
can be avoided. The amount is preferably in the range of 60 to 80
parts by mass.
[0053] As the aromatic vinyl compound (3), which is an essential
component of the hydrophilic copolymer (A), for example, styrene,
.alpha.-methylstyrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, ethylstyrene, vinylxylene, bromostyrene,
vinylbenzyl chloride, p-t-butylstyrene, chlorostyrene and
alkylstyrene are included.
[0054] In the present invention, one or more aromatic vinyl
compounds can be used.
[0055] Among these, from the viewpoint of ease of polymerization,
styrene is preferred.
[0056] The aromatic vinyl compound (3) is used in an amount of 3 to
20 parts by mass per 100 parts by mass of the unsaturated monomers
for use in the polymerization of hydrophilic copolymer (A). When
the amount is smaller than 20 parts by mass, satisfactory image
reproducibility and developability with aqueous developer solutions
can be attained. When the amount is larger than 3 parts by mass,
the components of photosensitive resin composition can be dispersed
in the mixture with satisfactory homogeneity. The amount is
preferably in the range of 5 to 20 parts by mass.
[0057] The alkyl (meth)acrylate (4), which is an essential
component of the hydrophilic copolymer (A), generally refers to an
alkyl acrylate and an alkyl methacrylate, and includes, for
example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl
(meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate,
isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamylhexyl
(meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl
(meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate,
cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl
(meth)acrylate, 2-ethylhexyl (meth)acrylate or hydroxylethyl
(meth)acrylate.
[0058] In the present invention, one or more alkyl (meth)acrylates
can be used.
[0059] Among these, from the viewpoint of easiness of synthesis,
ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate are
preferred.
[0060] The alkyl (meth)acrylate (4) is used in an amount of 3 to 30
parts by mass per 100 parts by mass of the unsaturated monomers for
use in the polymerization of hydrophilic copolymer (A). When the
amount is smaller than 30 parts by mass, excellent water resistance
can be attained. When the amount is larger than 3 parts by mass,
satisfactory developability with aqueous developer solutions can be
attained. The amount is preferably in the range of 5 to 25 parts by
mass.
[0061] In the hydrophilic copolymer (A), unsaturated monomers other
than the above components (1) to (4) that can be used, for example,
include a polyfunctional vinyl compound, ethylenic monocarboxylic
acid alkyl ester monomers having a hydroxyl group, unsaturated
dibasic acid alkyl esters, maleic anhydride, vinyl cyanide
compounds, (meth)acrylamide and its derivatives, vinyl esters,
vinyl ethers, vinyl halides, basic monomers having an amino group,
vinylpyridine, olefins, .alpha.,.beta.-ethylenic unsaturated
monomers, allyl compounds or reactive emulsifiers.
[0062] The polyfunctional vinyl compound which can be used, if
necessary, in the present invention refers to a monomer having two
or more vinyl bonds in a single molecule (provided that conjugated
diene monomers are excluded) and includes, for example, an aromatic
polyfunctional vinyl compound or a polyfunctional alkyl
(meth)acrylate.
[0063] The aromatic polyfunctional vinyl compounds, include, for
example, divinylbenzene or trivinylbenzene. The polyvinyl
(meth)acrylic acid esters include, for example, ethylene glycol
di(meth)acrylate, ethylene glycol di(meth)acrylate, 1,3-butylene
glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate,
propylene glycol di(meth)acrylate, 1,5-pentanediol
di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene
glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate,
polyethylene glycol di(meth)acrylate, polypropylene glycol
di(meth)acrylate, pentaerythritol tri(meth)acrylate,
trimethylolpropane tri(meth)acrylate, tetramethylolmethane
tetra(meth)acrylate, allyl (meth)acrylate,
bis(4-acryloxypolyethoxyphenyl- )propane, methoxypolyethylene
glycol (meth)acrylate, .beta.-(meth)acryloyloxyethyl hydrogen
phthalate, .beta.-(meth)acryloylox- yethyl hydrogen succinate,
3-chloro-2-hydroxypropyl (meth)acrylate, stearyl (meth)acrylate,
phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol
(meth)acrylate, 2-hydroxy-1,3-di(meth)acryloxypropane,
2,2-bis[4-((meth)acryloxyethoxy)phenyl]propane,
2,2-bis[4-((meth)acryloxy- .cndot.diethoxy)phenyl]propane or
2,2-bis[4-((meth)acryloxy.cndot.polyetho- xy)phenyl]propane.
Further, polyfunctional vinyl compounds having a hydrophilic group
are also included therein.
[0064] These compounds can be used either singly or in the
combination of two or more.
[0065] From the viewpoint of print wear characteristics and plate
wiping-off resistance, it is preferred that the amount of
polyfunctional vinyl compound is small. The amount thereof is
preferably 0.5 part by mass or less per 100 parts by mass of the
monomers for use in the hydrophilic copolymer (A).
[0066] The ethylenic monocarboxylic acid alkyl ester monomers
having a hydrolyl group include, for example, 2-hydroxyethyl
acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
2-hydroxypropyl methacrylate, 1-hydroxypropyl acrylate,
1-hydroxypropyl methacrylate and hydroxycyclohexyl
(meth)acrylate.
[0067] The unsaturated dibasic acid alkyl esters include, for
example, an alkyl crotonate, an alkyl itaconate, an alkyl fumarate
or an alkyl maleate.
[0068] The vinyl cyanide compounds include, for example,
acrylonitrile and methacrylonitrile.
[0069] The (meth)acrylamide or derivatives thereof include, for
example, (meth)acrylamide, N-methylol(meth)acrylamide and an
N-alkoxy(meth)acrylamide.
[0070] The vinyl esters include, for example, vinyl acetate, vinyl
butylate, vinyl stearate, vinyl laurate, vinyl myristate, vinyl
propionate and vinyl versatate.
[0071] The vinyl ethers include, for example, methyl vinyl ether,
ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl
vinyl ether and hexyl vinyl ether.
[0072] The vinyl halides include, for example, vinyl chloride,
vinyl bromide, vinyl fluoride, vinylidene chloride and vinylidene
fluoride.
[0073] The basic monomers having an amino group, include, for
example, aminoethyl (meth)acrylate, dimethylaminoethyl
(meth)acrylate or diethylaminoethyl (meth)acrylate.
[0074] The olefins include, for example, ethylene.
[0075] The .alpha.,.beta.-ethylenic unsaturated monomers containing
silicon, include, for example, vinyltrichlorosilane and
vinyltriethoxysilane.
[0076] These monomers can be used either singly or in mixtures of
two or more.
[0077] Although the method of polymerizing the hydrophilic
copolymer (A) for use in the present invention is not particularly
limited, emulsion polymerization is preferably employed. The
process of emulsion polymerization, for example, comprises
introducing beforehand given amounts of water, an emulsifier and
other additives into a reaction system whose temperature has been
adjusted to a temperature suitable for polymerization and
thereafter adding a polymerization initiator, monomers, an
emulsifier, a regulator, etc. to the reaction system in a
batch-wise manner or a continuous manner so as to effect
polymerization. It is also a commonly used method to, introduce
given amounts of a seed latex, an initiator, monomers and other
regulators into a reaction system in advance, if necessary. It is
also feasible to alter the layer structure of polymerized
hydrophilic copolymer particles in stages by employing a method
wherein unsaturated monomers, an emulsifier, other additives and a
regulator are added at later stages to the reaction system. As
properties representing the structure of each layer, for example,
hydrophilicity, glass transition temperature, molecular weight and
crosslinking density. With respect to the layer structure, the
number of stages therein is not particularly limited.
[0078] An emulsifier (surfactant) for use in the emulsion
polymerization is preferably, a reactive emulsifier from the
viewpoint of water resistance and print wear characteristics.
[0079] The reactive emulsifier which can be employed in the present
invention refers to an emulsifier (surfactant) that simultaneously
has a radically polymerizable double bond, a hydrophilic functional
group and a hydrophobic group in its molecular structure as well as
the emulsification, dispersion and wetting functions like common
emulsifiers, and that can synthesize a polymer having a particle
diameter of 5 to 500 nm, when it is used in an amount of 0.1 part
by mass or more per 100 parts by mass of unsaturated monomers other
than the reactive emulsifier upon polymerizing the hydrophilic
copolymer. Examples of the structure of radically polymerizable
double bonds contained in the molecular structure include a vinyl
group, an acryloyl group and a methacryloyl group. Examples of the
hydrophilic functional groups contained in the molecular structure
include anionic groups such as a sulfate group, a nitrate group, a
phosphate group, a borate group and a carboxyl group; cationic
groups such as an amino group; polyoxyalkylene chain structures
such as polyoxyethylene, polyoxymethylene and polyoxypropylene; and
a hydroxyl group. Examples of the hydrophobic groups contained in
the molecular structure include an alkyl group and a phenyl group.
These reactive emulsifiers include anionic emulsifiers, nonionic
emulsifiers, cationic emulsifiers, amphoteric emulsifiers, etc.,
depending on the type of structure of hydrophilic functional group
contained in the molecular structure. Moreover, the radically
polymerizable double bond, hydrophilic functional group and
hydrophobic group contained in the molecular structure thereof can
have a plurality of structure types and functional groups.
[0080] Specific examples of these reactive emulsifiers (reactive
surfactants) will be shown in (i) to (viii) below. 1
[0081] Trade name: Adeka Rea Soap SE1025 (Asahi Denka Kogyo K.K.)
2
[0082] Trade name: Aqualon HS1025 (Dai-ichi Kogyo Seiyaku Co.,
Ltd.) 3
[0083] Trade name: Latemul S-18OA (Kao Corp.) 4
[0084] Trade name: Antox MS-60 (Nippon Nyukazai Co., Ltd.) 5
[0085] Trade name: SDX-1050 (Asahi Denka Kogyo K.K.) 6
[0086] See JP-A-54(1979)-144317 7
[0087] Trade name: Aqualon RN20 (Dai-ichi Kogyo Seiyaku Co.,
Ltd.).
[0088] Among those which can be used as a reactive emulsifier in
the present invention, generally commercially available items
include, but are not limited to the following examples: as an
anionic surfactant, for example, Adeka Rea Soap SE (Asahi Denka
Kogyo K.K., trade name), Aqualon HS, or BC, or KH (Dai-ichi Kogyo
Seiyaku Co., Ltd., trade name), Latemul S (Kao Corp., trade name),
Antox MS (Nippon Nyukazai Co., Ltd., trade name), Adeka Rea Soap
SDX, or PP (Asahi Denka Kogyo K.K., trade name), Hitenol A
(Dai-ichi Kogyo Seiyaku Co., Ltd., trade name), Eleminol RS (Sanyo
Chemical Industries Ltd., trade name) or Spinomar (Tosoh
Corporation, trade name); as a nonionic surfactant, for example,
Aqualon RN or Noigen N (Dai-ichi Kogyo Seiyaku Co., Ltd., trade
name) or Adeka Rea Soap NE (Asahi Denka Kogyo K.K., trade name).
These emulsifiers may be used singly or in combination of two or
more.
[0089] It is preferred that the amount of reactive emulsifier used
in the emulsion polymerization is 1 part by mass or more from the
viewpoint of excellent image reproducibility, but 20 parts by mass
or less from the viewpoint of water resistance and print wear
characteristics, per 100 parts by mass of the unsaturated monomers
for use in the polymerization of hydrophilic copolymer (A).
[0090] In the present invention, a nonreactive emulsifier can be
used.
[0091] The nonreactive emulsifiers, include, for example, an
anionic surfactant such as a fatty acid soap, a rosin acid soap, a
sulfonic acid salt, a sulfate, a phosphoric acid ester, a
polyphosphoric acid ester or an acyl sarcosinate; or a cationic
surfactant such as a fat and oil derivative converted to nitrile, a
fat and oil derivative, a fatty acid derivative or an
.alpha.-olefin derivative; or a nonionic surfactant such as an
alcohol ethoxylate, an alkylphenol ethoxylate, a propoxylate, an
aliphatic alkanolamide, an alkylpolyglycoside, a polyoxyethylene
sorbitan fatty acid ester or an oxyethyleneoxypropylene block
copolymer.
[0092] The sulfonic acid salts include, for example, an alkyl
sulfonate, an alkyl sulfate, an alkyl sulfosuccinate, a
polyoxyethylene alkyl sulfate, a sulfonated fat and oil, an alkyl
diphenyl ether disulfonate, an .alpha.-olefin sulfonate, an alkyl
glyceryl ether sulfonate or an N-acylmethyltaurate salt.
[0093] It is preferred that the amount of nonreactive emulsifier
used in the emulsion polymerization is small from the viewpoint of
water resistance and hygroscopicity, for example, 1 part by mass or
less per 100 parts by mass of hydrophilic copolymer (A).
[0094] The reactive emulsifier and the nonreactive emulsifier can
be used in combination.
[0095] A known chain transfer agent can be used in the
polymerization of hydrophilic copolymer (A) for use in the present
invention. For example, chain transfer agents containing a sulphur
atom include alkanethiols, such as t-dodecylmercaptan and
n-dodecylmercaptan; thioalkyl alcohols, such as mercaptoethanol and
mercaptopropanol; thioalkylcarboxylic acids such as, thioglycolic
acid and thiopropionic acid; thiocarboxylic acid alkyl esters, such
as octyl thioglycolate and octyl thiopropionate; and sulfides such
as dimethyl sulfide or diethyl sulfide. In addition, examples of
the chain transfer agent, for example, halogenated hydrocarbons
such as terpinolene, dipentene, t-terpinene or carbon
tetrachloride. Among these chain transfer agents, an alkanethiol is
preferred from the viewpoint of high rate of chain transfer and
from the viewpoint that the balance among the properties of a
resulting polymer is desirable. These chain transfer agents can be
used singly or in mixture of two or more. These chain transfer
agents are either mixed with monomers before being fed into the
reaction system, or added singly in a given amount at a given
timing.
[0096] The amount of the chain transfer agent used is preferably
0.1 part by mass or more from the viewpoint of processability, but
10 parts by mass or less from the viewpoint of inhibiting a sharp
drop of molecular weight, per 100 parts by mass of the unsaturated
monomers for use in the polymerization of hydrophilic copolymer
(A).
[0097] In the polymerization of the hydrophilic copolymer (A) for
use in the present invention, a polymerization reaction retarder
can be used, if necessary. The polymerization reaction retarder
refers to a compound which lowers the rate of radical
polymerization when added to an emulsion polymerization system.
More specifically, it refers to a polymerization rate retarder, a
polymerization inhibitor, a chain transfer agent with low radical
re-initiation reactivity or a monomer with low radical
re-initiation reactivity. The polymerization reaction retarder is
used for adjusting polymerization reaction rate and for adjusting
latex properties. This polymerization reaction retarder is added to
the reaction system in a batchwise or continuous manner. When the
polymerization reaction retarder is used, the strength of latex
film tends to increase. Although the details of reaction mechanism
has not yet been elucidated, it is believed that the polymerization
reaction retarder is closely associated with the steric
configuration of polymer, and hence it is presumed that the
polymerization reaction retarder is effective in adjusting latex
film properties. Examples of the polymerization reaction retarder
include quinones, such as o-, m- and p-benzoquinones; nitro
compounds, such as nitrobenzene or o-, m- or p-dinitrobenzene;
amines, such as diphenylamine; catechol derivatives, such as
t-butylcatechol; 1,1-disubstituted vinyl compounds such as
1,1-diphenylethylene, .alpha.-methylstyrene or
2,4-diphenyl-4-methyl-1-pentene; or 1,2-disubstituted vinyl
compounds such as 2,4-diphenyl-4-methyl-2-pentene or cyclohexene.
In addition, the polymerization reaction retarders include the
compounds described as a polymerization inhibitor or polymerization
retarder in "POLYMER HANDBOOK 3rd Ed. (J. Brandup, E. H. Immergut:
John Wiley & Sons, 1989)" and "Kaitei Kobunshi Gosei No Kagaku
(Revised: Chemistry of Polymer Synthesis) (Otsu, Kagaku Dojin,
1979)". Among these polymerization reaction retarders,
2,4-diphenyl-4-methyl-1-pe- ntene (.alpha.-methylstyrene dimer) is
especially preferred from the viewpoint of reactivity. These
polymerization reaction retarders can be used either singly or in
mixture of two or more.
[0098] The amount of polymerization reaction retarder used is
preferably 10 parts by mass or less per 100 parts by mass of the
unsaturated monomers for use in the polymerization of hydrophilic
copolymer (A) from the viewpoint of suppressing the sharp drop of
polymerization rate.
[0099] The radical polymerization initiator for use in the emulsion
polymerization refers to a compound which undergoes a radical
decomposition under heating or in the presence of a reducing
substance to initiate the addition polymerization of monomers. Both
an inorganic initiator and an organic initiator can be used.
Examples of the radical polymerization initiator include,
water-soluble or oil-soluble peroxodisulfuric acid salts,
peroxides, azobis compounds and the like. More specifically, for
example, potassium peroxodisulfate, sodium peroxodisulfate,
ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide,
benzoyl peroxide, 2,2-azobisbutyronitrile, cumene hydroperoxide and
the like are included. In addition, further examples of the radical
polymerization initiators include the compounds described in
"POLYMER HANDBOOK 3rd Ed. (J. Brandrup and E. H. Immergut,
published by John Wiley & Sons (1989)". Also, the so-termed
redox polymerization method wherein the polymerization initiator is
used in combination with a reducing agent, such as acidic sodium
sulfite, ascorbic acid or its salt, erythorbic acid or a salt
thereof, or rongalite, can be employed. Among the above
polymerization initiators, peroxodisulfuric acid salts are
especially preferred.
[0100] The amount of polymerization initiator used is preferably
0.2 part by mass or more from the viewpoint of stability during
polymerization, but 3 parts by mass or less from the viewpoint of
antihygroscopicity of resin composition, per 100 parts by mass of
unsaturated monomers for use in the polymerization of hydrophilic
copolymer (A).
[0101] In the present invention, various polymerization regulators
can be added, if necessary. For example, sodium hydroxide,
potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate,
sodium carbonate or disodium hydrogen phosphate can be added as a
pH regulator. Further, various chelating agents such as sodium
ethylenediaminetetraacetate can be added as a polymerization
regulator. Still further, various additives, for example, a
viscosity lowering agent such as an alkali-functioned latex or
hexametaphosphoric acid, a water-soluble polymer such as polyvinyl
alcohol or carboxymethylcellulose, a thickener, various age
resisters, an ultraviolet absorber, an antiseptic, a germicide, a
defoamer, a dispersant such as sodium polyacrylate, a waterproofing
agent, a metal oxide such as zinc oxide, a crosslinking agent such
as an isocyanate compound or an epoxy compound, a lubricant and a
water retainer may be added as other additives. The method of
adding these additives is not particularly limited, and the
addition can be effected irrespective of being during the
polymerization or after the polymerization of hydrophilic
copolymer.
[0102] The polymerization temperature at which the emulsion
polymerization is performed is preferably 60.degree. C. or higher
from the viewpoint of developability with aqueous developer
solution, print wear characteristics and plate wiping-off
resistance, but 120.degree. C. or below from the viewpoint of
avoiding the difficulty in production due to a pressure increase
during the polymerization. More preferably, the temperature is in
the range of 70 to 120.degree. C.
[0103] The number average particle diameter of obtained hydrophilic
copolymer (A) is preferably in the range of 5 to 500 nm. The number
average particle diameter is preferably 500 nm or less from the
viewpoint of developability with aqueous developer solution and
image reproducibility, but 5 nm or more from the viewpoint of print
wear characteristics. More preferably, the number average particle
diameter is in the range of 5 to 100 nm.
[0104] The toluene gel ratio of obtained hydrophilic copolymer (A)
is preferably in the range of 60 to 99%. The toluene gel ratio is
preferably 80% or higher from the viewpoint of printing plate
strength and print wear characteristics, but 95% or below from the
viewpoint of compatibility (miscibility), processability and
developability with aqueous developer solution of photosensitive
resin.
[0105] The toluene gel ratio is determined in the following manner.
An appropriate amount of a dispersion of about 30 wt %
concentration obtained by an emulsion polymerization of hydrophilic
copolymer (A) is dropped on a polytetrafluoroethylene sheet and
dried at 130.degree. C. for 30 min. 0.5 g of dried hydrophilic
copolymer (A) is collected, immersed in 30 ml of 25.degree. C.
toluene, shaken with the use of a shaker for 3 hr and filtered
through a 320 SUS mesh. Matter not having passed through the mesh
is dried at 130.degree. C. for 1 hr and weighed. The toluene gel
ratio is defined as a weight fraction (%) obtained by dividing the
above weight by 0.5 (g).
[0106] The ratio of the amount of hydrophilic copolymer (A) to the
total amount of photosensitive resin composition for flexographic
printing is preferably 20 wt % or larger from the viewpoint of
developability with aqueous developer solution, but 60 wt % or
smaller from the viewpoint of suppression of hygroscopicity and
water resistance and ink swelling resistance.
[0107] The thermoplastic elastomer (B) for use in the present
invention refers to an elastomer which exhibits rubber elasticity
at about room temperature and is resistant to plastic deformation
and which is plasticized by heat upon mixing the composition by
means of, for example, an extruder. The thermoplastic elastomers
include, for example, a thermoplastic block copolymer,
1,2-polybutadiene and a polyurethane-type elastomer.
[0108] Among these thermoplastic elastomers, the thermoplastic
block copolymer is preferred. In particular, a thermoplastic block
copolymer obtained by polymerizing a monovinyl substituted aromatic
hydrocarbon monomer and a conjugated diene monomer is more
preferred. For example, styrene, .alpha.-methylstyrene,
p-methylstyrene or p-methoxystyrene can be used as the monovinyl
substituted aromatic hydrocarbon monomer. For example, butadiene or
isoprene can be used as the conjugated diene monomer.
Representative examples of thermoplastic block copolymers include a
styrene-butadiene-styrene block copolymer and a
styrene-isoprene-styrene block copolymer. The content of monovinyl
substituted aromatic hydrocarbon in the thermoplastic elastomer is
preferably 8 wt % or more from the viewpoint of suppression of the
cold flow resistance exhibited in laminating of photosensitive
resin plates before exposure, but 50 wt % or less from the
viewpoint of suppression of the deterioration of printing quality
attributed to an excessive increase of printing plate hardness.
[0109] The average proportion of vinyl bonds in the conjugated
diene segment of the thermoplastic elastomer is preferably 5% or
higher from the viewpoint of image reproducibility of printing
plate, but 40% or lower from the viewpoint of suppression of
printing plate surface stickiness. The average proportion is more
preferably in the range of 10 to 35%.
[0110] The average contents of monovinyl substituted aromatic
hydrocarbon and conjugated diene and the average proportion of
vinyl bond units in the thermoplastic elastomer can be determined
by IR spectroscopy or NMR.
[0111] The amount of thermoplastic elastomer (B) used, based on the
total amount of photosensitive resin composition for flexographic
printing, is preferably 10 wt % or more from the viewpoint of
excellent physical properties (elongation (extension)) of printing
plates and also water resistance and ink swelling resistance
thereof, but 40 wt % or less from the viewpoint of developability
with aqueous developer solutions.
[0112] The photopolymerizable unsaturated monomer (C) for use in
the present invention may be, for example, any of esters of acrylic
acid, methacrylic acid, fumaric acid and maleic acid; derivatives
of acrylamide and methacrylamide; allyl esters, styrene and
derivatives thereof; and N-substituted maleimide compounds.
[0113] Specific examples thereof include diacrylates and
dimethacrylates of alkanediols such as hexanediol and nonanediol;
diacrylates and dimethacrylates of ethylene glycol, diethylene
glycol, propylene glycol, dipropylene glycol, polyethylene glycol
and butylene glycol; trimethylolpropane triacrylate or
trimethacrylate and pentaerythritol tetraacrylate or
tetramethacrylate; N,N'-hexamethylenebisacrylamide or
-methacrylamide; and styrene, vinyltoluene, divinylbenzene,
diacrylphthalate, triallyl cyanurate, diethyl fumarate, dibutyl
fumarate, dioctyl fumarate, distearyl fumarate, butyl octyl
fumarate, diphenyl fumarate, dibenzyl fumarate, dibutyl maleate,
dioctyl maleate, bis(3-phenylpropyl) fumarate, dilauryl fumarate,
dibehenyl fumarate and N-laurylmaleimide. These may be used singly
or in combination of two or more.
[0114] The amount of photopolymerizable unsaturated monomer (C)
used, based on the total amount of photosensitive resin composition
for flexographic printing, is preferably 1 wt % or more from the
viewpoint of capability of forming fine dots or characters, but 30
wt % or less from the viewpoint of resistance to cold flow
exhibited upon laminating photosensitive resin plates before
exposure and from the viewpoint of suppression of the deterioration
of printing quality attributed to an excessive increase of printing
plate hardness.
[0115] Examples of the photopolymerization initiator (D) for use in
the present invention include, for example, benzophenone,
4,4-bis(diethylamono)-benzophenone, t-butylanthraquinone and
2-ethylanthraquinone; thioxanthones such as
2,4-diethylthioxanthone, isopropylthioxanthone and
2,4-dichlorothioxanthone; acetophenones such as
diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one,
benzyldimethylketal, 1-hydroxycyclohexyl-phenylketone,
2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoin
ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin
isopropyl ether and benzoin isobutyl ether; acylphosphine oxides
such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide,
bis(2,6-dimethoxybenzoyl)-- 2,4,4-trimethylpentylphosphine oxide
and bis(2,4,6-trimethylbenzoyl)-pheny- lphosphine oxide;
methylbenzoyl formate; 1,7-bisacridinylheptane; and
9-phenylacridine. These can be used singly or in combination.
[0116] The amount of photopolymerization initiator (D) used, based
on the total amount of photosensitive resin composition, is
preferably in the range of 0.1 to 10 wt %. The amount is preferably
0.1 wt % or more from the viewpoint of capability of forming fine
dots or characters, but 10 wt % or less from the viewpoint of
exposure sensitivity lowering attributed to a drop of transmittance
of actinic rays such as ultraviolet radiation.
[0117] To the photosensitive resin composition of the present
invention, if necessary, various supplementary additives, such as
plasticizers, thermal polymerization inhibitors, ultraviolet
absorbers, antihalation agents and photostabilizers, can be added
in addition to the above essential components.
[0118] The plasticizer is a liquid having fluidity at room
temperature, and can be, for example, hydrocarbon oils such as
naphthenic oil and paraffinic oil, liquid polybutadiene, liquid
polyisoprene, liquid polybutadiene modification products, liquid
acrylonitrile-butadiene copolymer, liquid styrene-butadiene
copolymer, polystyrene of 2,000 or less number average molecular
weight, sebacic acid esters and phthalic acid esters. These
components may have photopolymerizable reactive groups.
[0119] For maintaining the precision of printing plate, the
photosensitive resin composition of the present invention may be
provided with a support of, for example, polyester on the side
opposite to relief. Because the photosensitive resin composition of
the present invention may be sticky depending on the composition
thereof, a flexible film layer which can be developed with an
aqueous developer solution may be provided on a surface of the
photosensitive resin composition so as to improve the contact with
a negative film superimposed thereon and so as to make
reutilization of the negative film possible.
[0120] The photosensitive resin composition of the present
invention can be produced by blending the above components (A) to
(D) by means of, for example, an extruder or a kneader. The
photosensitive resin composition after blending can be formed into
a layer with a desired thickness by hot press molding, or
calendering, or extrusion.
[0121] A support or flexible film layer can be closely contacted to
the photosensitive layer by roll laminating after sheeting. After
the laminating, hot pressing may be performed so as to obtain the
photosensitive layer with higher precision.
[0122] An actinic ray source for use in photohardening of the
photosensitive resin composition of the present invention may be,
for example, a low pressure mercury lamp, a high pressure mercury
lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a xenon
lamp, a zirconium lamp or sunlight.
[0123] The photosensitive resin composition of the present
invention is exposed to light through a negative film so as to form
an image. Thereafter, unexposed portion is removed (developed) with
the use of an aqueous developer solution, so that a relief can be
obtained.
[0124] The aqueous developer solution for use in the present
invention is obtained by adding to water a surfactant such as a
nonionic or an anionic surfactant and, if necessary, a pH
regulator, a washing accelerator, etc. Specific examples of the
nonionic surfactant include, for example, a polyoxyalkylene alkyl
or alkenyl ether, a polyoxyalkylene alkyl or alkenyl phenyl ether,
a polyoxyalkylenealkyl (or alkenyl)amine, a polyoxyalkylenealkyl
(or alkenyl)amide and an ethylene oxide/propylene oxide block
adduct. Specific examples of the anionic surfactant include, for
example, a linear alkylbenzene sulfonate having an alkyl having 8
to 16 carbon atoms on the average, an .alpha.-olefin sulfonate
having 10 to 20 carbon atoms on the average, a dialkyl
sulfosuccinate having an alkyl or alkenyl having 4 to 10 carbon
atoms, a sulfonate of fatty acid lower alkyl ester, an alkyl
sulfate having 10 to 20 carbon atoms on the average, an alkyl ether
sulfate having a linear or branched chain alkyl or alkenyl having
10 to 20 carbon atoms on the average and having an average 0.5 to 8
mol of ethylene oxide added, and a saturated or unsaturated fatty
acid salt having 10 to 22 carbon atoms on the average.
[0125] The pH regulator is preferably, for example, a borate, a
carbonate, a silicate, a metasilicate, a succinate or an acetate.
In particular, sodium silicate is preferred from the viewpoint of
high solubility in water.
[0126] Furthermore, a washing auxiliary can be used. The use
thereof in combination with the above surfactants and pH regulators
enhances washing capacity. Specific examples of the washing
auxiliary include amines such as monoethanolamine, diethanolamine
and triethanolamine; ammonium salts such as tetramethylammonium
hydroxide; glycol ethers; and paraffinic hydrocarbons.
[0127] These washing auxiliaries are added to water in an
appropriate mixing ratio ranging from 0.1 to 50 wt %, preferably
from 0.2 to 10 wt % and mixed before use.
[0128] Still further, if necessary, these washing auxiliaries may
be used in combination with a defoamer, a dispersant, a corrosion
inhibitor and an antiseptic agent.
[0129] After the development, the obtained plate is generally dried
in an oven at about 60.degree. C. for 15 to 120 min.
[0130] The photosensitive resin composition of the present
invention, depending on the composition thereof, may have
stickiness on the plate surface even after the drying. Such
stickiness can be eliminated by a known surface treatment. As a
preferred surface treatment, there can be mentioned an exposure to
actinic rays of 300 nm or less wavelength.
[0131] The present invention will be described in details below
with reference to the following Production Examples, Working
Examples and Comparative Examples.
PRODUCTION EXAMPLES
[0132] Polymerization of Hydrophilic Copolymer (A)
Production Example 1
[0133] Polymerization of Hydrophilic Copolymers (A) as in Examples
1 to 18 and Comparative Examples 1 to 7 in Tables 1 to 4 and in
Examples 20 to 22 in Table 5
[0134] 125 parts by mass of water and 3 parts by mass, out of the
total amount indicated in the Tables, of emulsifier were initially
introduced into a pressure reaction vessel equipped with an
agitator and a jacket for temperature control. The internal
temperature of the pressure reaction vessel was raised to
80.degree. C., and an oily mixed liquid consisting of a mixture of
monomers in proportions listed in Tables 1 to 5 and
t-dodecylmercaptan and an aqueous solution consisting of 28 parts
by mass of water, 1.2 parts by mass of sodium peroxodisulfate, 0.2
part by mass of sodium hydroxide and the rest of emulsifier
indicated in the Tables, i.e. 1 part by mass, were added at
constant flow rate over periods of 5 hr and 6 hr, respectively. The
temperature of 80.degree. C. was maintained for 1 hr so as to
complete the polymerization reaction, and the reaction mixture was
cooled. The pH value of the thus formed copolymer latex was
adjusted to 7 with sodium hydroxide, and unreacted monomers were
removed by steam stripping. The copolymer latex was filtered
through a 200-mesh metal net. In this manner, the copolymer was
adjusted to have the final solids content of 40 wt % in order to
obtain the hydrophilic copolymer (A) solution.
[0135] The solutions after emulsion polymerization were dried at
60.degree. C., thereby obtaining the intended hydrophilic
copolymers.
Production Example 2
[0136] Polymerization of Hydrophilic Copolymer (A) of Example 19 in
Table 5
[0137] The hydrophilic copolymer (A) was obtained in the same
manner as in Production Example 1, except that 1 part by mass, out
of the total amount shown in the Table, of the reactive emulsifier
was initially introduced into the pressure reaction vessel while
the rest of the reactive emulsifier, i.e. 1 part by mass, was added
in the form of an aqueous solution.
Production Example 3
[0138] Polymerization of Hydrophilic Copolymer (A) of Example 23 in
Table 5
[0139] The hydrophilic copolymer (A) was obtained in the same
manner as in Production Example 1, except that 13.5 parts by mass,
out of the total amount shown in the Table, of the reactive
emulsifier was initially introduced into the pressure reaction
vessel while the rest of the reactive emulsifier, i.e. 1.5 parts by
mass, was added in the form of an aqueous solution.
Production Example 4
[0140] Polymerization of Hydrophilic Copolymer (A) of Example 24 in
Table 5
[0141] The hydrophilic copolymer (A) was obtained in the same
manner as in Production Example 1, except that 3 parts by mass, out
of the total amount shown in the Table, of the reactive emulsifier,
and 0.5 part by mass of the nonreactive emulsifier were initially
introduced into the pressure reaction vessel while the rest of the
reactive emulsifier, i.e. 1 part by mass, was added in the form of
an aqueous solution.
Examples 1 to 24 and Comparative Examples 1 to 7)
[0142] (1) Preparation of Photosensitive Resin Composition and
Photosensitive Resin Plate
[0143] 35 parts by mass of each of the hydrophilic copolymers (A)
obtained in the Production Examples 1 to 4 and 25 parts by mass of
styrene butadiene block copolymer (Crayton D-KX405 produced by
Shell Chemicals) were blended together by means of a pressure
kneader at 140.degree. C. for 10 min. Thereafter, 30 parts by mass
of liquid polybutadiene (B-2000 produced by Nippon Petrochemicals
Co., Ltd.), 5 parts by mass of 1,6-hexanediol diacrylate, 5 parts
by mass of 1,6-hexanediol dimethacrylate, 2 parts by mass of
2,2-dimethoxyphenylacetophenone and 1 part by mass of
2,6-di-t-butyl-p-cresol were added little by little over a period
of 15 min. After the completion of addition, the mixture was
further kneaded for 10 min to obtain photosensitive resin
compositions.
[0144] Each of the photosensitive resin compositions was taken out,
sandwiched between a 100 .mu.m thick polyester film (hereinafter
simply referred to as "PET") coated with a thermoplastic elastomer
based adhesive on one side and a 100 .mu.m thick PET coated with a
5 .mu.m thick polyvinyl alcohol (PVA) on the other side, and formed
into a 3 mm thick sheet by means of a press at 130.degree. C.
[0145] (2) Preparation of Printing Plate
[0146] Each of the sheets obtained in item (1) above, was exposed
to ultraviolet light from the side of the adhesive-coated PET, by
means of ultraviolet exposer (JE-A2-SS manufactured by Nippon
Denshi Seiki) so that the thickness of cured layer was about 1.8
mm. Subsequently, the PVA-coated PET was peeled in such a manner
that PVA remained on the resin surface, and a negative film bearing
an image to be printed was closely contacted thereto and exposed by
means of the above exposer for 10 min. After the exposure, the
negative film was detached, and the cured layer was washed with a
separately prepared aqueous solution containing 5 wt % of
polyoxyalkylene alkyl ether, 2 wt % of sodium borate and 0.7 wt %
of paraffin having 10 carbon atoms (aqueous developer solution) at
40.degree. C. by means of washer (JOW-A3-P) manufactured by Nippon
Denshi Seiki so as to remove unexposed portions. Drying and
thereafter post-exposure by means of an ultraviolet germicidal
radiation lamp and an ultraviolet chemical lamp were performed.
Thus, printing plates were obtained.
[0147] (3) Method of Evaluation
[0148] (a) Compatibility (Dispersibility)
[0149] Each mixture of photosensitive resin composition was
visually inspected for any remaining particles. When any particles
were observed, the compatibility was judged as x. When no particles
were observed, the compatibility was judged as .largecircle.. With
respect to the mixtures having been judged as x, the following
evaluations were not carried out.
[0150] (b) Developability by Aqueous Developer Solution
[0151] An unexposed resin plate was washed with the above aqueous
developer solution in the above washer for 15 min. The resin plate
thickness (t) reduced by the washing was measured, and 15 min/t
(mm) was calculated, thereby determining the time (min) required
for development of 1 mm. The shorter the developing time, the
greater the advantage. The developing time was judged as
.circleincircle. when 17 min/mm or less; judged as .largecircle.
when less than 20 min/mm; and judged as x when 20 min/mm or
more.
[0152] (c) Image Reproducibility
[0153] The image reproducibility of each printing plate was
evaluated by assessing through a microscope the configuration of
500 .mu.m depressed fine lines and protrudent fine lines with
respect to each relief image. The image reproducibility was judged
as .largecircle. when the groove of depressed fine lines was deep
and further the protrudent fine lines were sharp and free from
thickening; and judged as x when the groove of depressed fine lines
was shallow and/or the protrudent fine lines were not sharp and
thickened.
[0154] (d) Water Resistance (Water Swelling Ratio)
[0155] Each printing plate was immersed in water for 24 hr, and the
increment (%) from the weight before the immersion was calculated.
The smaller the increment, the greater the advantage. The swelling
ratio was judged as being acceptable when 1.3% or less.
[0156] (e) Print Wear Characteristics after Attachment of and
Swelling with Aqueous Base Ink
[0157] The surface strength of printing plate (print wear
characteristics) was evaluated by simultatively applying an
abrasion wheel (hard abrasion wheel, Taber abrader manufactured by
Tester Sangyo Co., Ltd.). A printing plate with overall solid
surface was prepared and immersed in a 10% aqueous isopropyl
alcohol solution as a substitute for water base ink for 16 hr. The
abrasion wheel was applied to the printing plate after immersion,
and rotated 1000 times. The abrasion loss of the printing plate was
measured. The abrasion loss was calculated by dividing the loss in
weight by the area of the abrasion wheel that was in contact with
the solid surface. The abrasion loss was judged as .circleincircle.
when 7 mg/cm.sup.2 or less; judged as .largecircle. when less than
10 mg/cm.sup.2; and judged as x when 10 mg/cm.sup.2 or more.
[0158] (f) Plate Wiping-Off Resistance
[0159] Herein, the terminology "plate wiping-off resistance" refers
to the degree of resistance of printing plate to damaging of image
portions in a printing plate, in the operation for wiping off the
water base ink from the printing plate.
[0160] The degree of plate wiping-off resistance was measured
simulatively, as shown in FIG. 1. Printing plate 1 (top view)
having 8 to 12 point-large characters was prepared by using
negative film 2. The printing plate 1 was immersed in a 10% aqueous
isopropyl alcohol solution as a substitute for water base ink for
16 hr, and thereafter rubbed from side to side 300 times by means
of NP print wear characteristics tester (manufactured by Niimura
Printing Co., Ltd., item brought into contact 3: 8 cm.times.6 cm
cloth, load: 1 kg). The degree of damage to the characters after
the rubbing was observed through a microscope. In the evaluation of
the plate wiping-off resistance of printing plate, the plate
wiping-off resistance was judged as .largecircle. when the
characters were not damaged, and judged as x when the characters
were damaged. However, with respect to the printing plates having
been judged as x in image reproducibility, the evaluation was
omitted.
[0161] The evaluation test results of the physical properties
obtained in the above methods are shown in Tables 1 and 2. In
overall evaluation, .largecircle. means being acceptable with
respect to all the evaluation items (a) to (f). The obtained
results will be described below with respect to the Examples and
Comparative Examples.
[0162] A summary of the evaluation test results of resin
compositions and printing plates obtained in Examples 1 to 5 and
Comparative Examples 1 and 2 are listed in Table 1.
[0163] It is apparent from Table 1 that when the proportion of
unsaturated monomer having a carboxyl group (1) is too low, the
developing time would be prolonged, and that when the proportion of
unsaturated monomer having a carboxyl group (1) is too high, not
only the water resistance but also, due to an increase of the
abrasion loss at ink attachment, the print wear characteristics
would be deteriorated.
1 TABLE 1 Example Example Example Example Example Comp. Comp. 1 2 3
4 5 Ex. 1 Ex. 2 (A) Composition of hydrophilic copolymer (pts. wt.)
(1) acrylic acid 2 2 5 2 2 1 2 (1) methacrylic acid 5 5 0 10 5 0 15
(1) itaconic acid 1 Sodium methacrylsulfonate *1 2 (2) butadiene 60
60 60 60 60 60 60 (3) styrene 15 15 15 12 15 15 15 (4) butyl
acrylate 18 17 20. 16 16 24 8 Total amt. of emulsifier (emulsifier:
(i) *2) 4 4 4 4 4 4 4 t-Dodecylmercaptan 2.0 2.0 2.0 2.0 2.0 2.0
2.0 Emulsion polymn. temp. (.degree. C.) 80 80 80 80 80 80 80 No.
av. particle diam. of copolymer (A) (nm) 57 48 55 48 45 58 47
Toluene gel ratio (%) 88 87 88 88 89 87 91 Evaluation (a)
compatibility (dispersibility) .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. (b) developability with aqueous developer
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
.circleincircle. X .circleincircle. solution *3 (c) image
reproducibility .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. X X (d) water swelling ratio (water
resistance) (%) *4 1.0 1.0 1.3 1.2 1.2 1.0 1.5 (e) print wear
characteristics *5 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
X (f) plate wiping-off resistance .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. Evalua- Evalua- tion tion
omitted omitted Overall evaluation *6 .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. X X *1 Produced by Asahi
Kasei Fine Chemical, trade name SMAS. *2 Emulsifier: (i) means
emulsifier (i) specified on page 20 of this specification. *3
Developing time: 17 min/mm or less .circleincircle., less than 20
min/mm .largecircle., and 20 min/mm or more X. *4 Water swelling
ratio when 1.3% or less was regarded as being acceptable. *5
Abrasion loss: 7 mg/cm.sup.2 or less .circleincircle., less than 10
mg/cm.sup.2 .largecircle., and 10 mg/cm.sup.2 or more X. *6
.largecircle. means being acceptable with respect to all the
evaluation items (a) to (f).
[0164] A summary of the evaluation test results of resin
compositions and printing plates obtained in Examples 1, 6 and 7
and Comparative Examples 3 and 4 are listed in Table 2.
[0165] It is apparent from Table 2 that when the proportion of
styrene is too low, the compatibility would be deteriorated, and
that when the proportion of styrene is too high, the developing
time would be prolonged and the image reproducibility would be
deteriorated.
[0166] In Comparative Example 3, because the compatibility was low
and a number of white particles were observed by visual inspection,
other evaluations were omitted.
2 TABLE 2 Exam- Exam- Exam- Comp. Comp. ple 1 ple 6 ple 7 Ex. 3 Ex.
4 (A) Composition of hydrophilic copolymer (pts. wt.) (1) acrylic
acid 2 2 2 2 2 (1) methacrylic acid 5 5 5 5 5 (2) butadiene 60 60
65 60 60 (3) styrene 15 10 5 1 30 (4) butyl acrylate 18 23 23 32 3
Total amt. of 4 4 4 4 4 emulsifier (emulsifier: (i) *1)
t-Dodecylmercaptan 2.0 2.0 2.0 2.0 2.0 Emulsion polymn. temp. 80 80
80 80 80 (.degree. C.) No. av. particle diam. of 57 59 62 63 45
copolymer (A) (nm) Toluene gel ratio (%) 88 87 86 85 90 Evaluation
(a) compatibility .largecircle. .largecircle. .largecircle. X
.largecircle. (dispersibility) (b) developability with
.circleincircle. .circleincircle. .circleincircle. Evalua- X
aqueous developer tion solution *2 omitted (c) image .largecircle.
.largecircle. .largecircle. Evalua- X reproducibility tion omitted
(d) water swelling ratio 1.0 1.0 1.0 Evalua- 1.0 (water resistance)
tion (%) *3 omitted (e) print wear .circleincircle.
.circleincircle. .circleincircle. Evalua- .circleincircle.
characteristics *4 tion omitted (f) plate wiping-off .largecircle.
.largecircle. .largecircle. Evalua- Evalua- resistance tion tion
omitted omitted Overall evaluation *5 .largecircle. .largecircle.
.largecircle. X X *1 Emulsifier: (i) means emulsifier (i) specified
on page 20 of this specification. *2 Developing time: 17 min/mm or
less .circleincircle., less than 20 min/mm .largecircle., and 20
min/mm or more X. *3 Water swelling ratio when 1.3% or less was
regarded as being acceptable. *4 Abrasion loss: 7 mg/cm.sup.2 or
less .circleincircle., less than 10 mg/cm.sup.2 .largecircle., and
10 mg/cm.sup.2 or more X. *5 .largecircle. means being acceptable
with respect to all the evaluation items (a) to (e).
[0167] A summary of the evaluation test results of resin
compositions and printing plates obtained in Examples 1 and 8 to 11
and Comparative Examples 5 to 7 are listed in Table 3.
[0168] It is apparent from Table 3 that when the proportion of
butadiene is too low, the water resistance and the print wear
characteristics when ink is adhered would be deteriorated. It is
also apparent that when the proportion of alkyl (meth)acrylate is
too low, the developability with aqueous developer solution would
be deteriorated, and that when the proportion of alkyl
(meth)acrylate is too high, the water resistance and print wear
characteristics would be deteriorated.
3 TABLE 3 Example Example Example Example Example Comp. Comp. Comp.
1 8 9 10 11 Ex. 5 Ex. 6 Ex. 7 (A) Composition of hydrophilic
copolymer (pts. wt.) (1) acrylic acid 2 3 2 2 2 2 2 2 (1)
methacrylic acid 5 4 5 5 5 5 5 1 (2) butadiene 60 70 55 60 60 30 75
55 (3) styrene 15 10 15 15 15 15 17 7 (4) butyl acrylate 18 13 23
48 1 35 (4) ethyl acrylate 18 (4) 2-ethylhexyl acrylate 18 Total
amt. of emulsifier (emulsifier: (i) *1) 4 4 4 4 4 4 4 4
t-Dodecylmercaptan 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Emulsion polymn.
temp. (.degree. C.) 80 80 80 80 80 80 80 80 No. av. particle diam.
of copolymer 57 51 60 55 50 61 58 52 (A) (nm) Toluene gel ratio (%)
88 90 87 88 88 86 89 89 Evaluation (a) compatibility
(dispersibility) .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. (b) developability with aqueous developer
.circleincircle. .smallcircle. .circleincircle. .circleincircle.
.circleincircle. X X .circleincircle. solution *2 (c) image
reproducibility .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. X .largecircle. .largecircle. (d) water
swelling ratio (water resistance) 1.0 0.9 1.1 1.1 1.0 1.5 1.1 1.5
(%) *3 (e) print wear characteristics *4 .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
X .largecircle. X (f) plate wiping-off resistance .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. Evalua-
.largecircle. X tion omitted Overall evaluation *5 .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. X X X *1
Emulsifier: (i) means emulsifier (i) specified on page 20 of this
specification. *2 Developing time: 17 min/mm or less
.circleincircle., less than 20 min/mm .largecircle., and 20 min/mm
or more X. *3 Water swelling ratio when 1.3% or less was regarded
as being acceptable. *4 Abrasion loss: 7 mg/cm.sup.2 or less
.circleincircle., less than 10 mg/cm.sup.2 .largecircle., and 10
mg/cm.sup.2 or more X. *5 .largecircle. means being acceptable with
respect to all the evaluation items (a) to (f).
[0169] With respect to Examples 1, 10 and 11, it is also apparent
from Table 3 that satisfactory results can be obtained in all the
evaluation tests, irrespective of the employed acrylate being butyl
acrylate, ethyl acrylate or 2-ethylhexyl acrylate.
[0170] A summary of the evaluation test results of resin
compositions and printing plates obtained in Examples 12 to 18 are
listed in Table 4.
[0171] Table 4 shows that satisfactory performance can be obtained
at varied polymerization temperatures and gel ratios. However,
specifically, it was found that when the polymerization temperature
was lowered, the developability with aqueous developer solution
tended to drop, and that when the gel ratio was low, not only the
developability with aqueous developer solution but also the print
wear characteristics tended to drop.
4 TABLE 4 Example Example Example Example Example Example Example
12 13 14 15 16 17 18 (A) Composition of hydrophilic copolymer (pts.
wt.) (1) acrylic acid 2 2 2 2 2 2 2 (1) methacrylic acid 5 5 5 5 5
5 5 (2) butadiene 60 60 60 60 60 60 60 (3) styrene 10 10 10 10 10
9.7 10 (4) butyl acrylate 23 23 23 23 23 23 23 divinylbenzene 0.3
Total amt. of emulsifier (emulsifier: (i) *1) 4 4 4 4 4 4 4
t-Dodecylmercaptan 1.6 1.7 1.9 2.4 1.7 2.4 3.3 Emulsion polymn.
temp. (.degree. C.) 60 70 80 100 80 80 80 No. av. particle diam. of
copolymer (A) (nm) 62 59 47 42 43 44 45 Toluene gel ratio (%) 89 89
90 91 92 89 75 Evaluation (a) compatibility (dispersibility)
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. (b) developability with
aqueous developer .largecircle. .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .largecircle.
solution *2 (c) image reproducibility .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. (d) water swelling ratio (water resistance) (%) *3
1.2 1.0 1.0 1.2 1.1 0.9 1.2 (e) print wear characteristics *4
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .largecircle. (f) plate
wiping-off resistance .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. Overall
evaluation *5 .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. *1
Emulsifier: (i) means emulsifier (i) specified on page 20 of this
specification. *2 Developing time: 17 min/mm or less
.circleincircle., less than 20 min/mm .largecircle., and 20 min/mm
or more X. *3 Water swelling ratio when 1.3% or less was regarded
as being acceptable. *4 Abrasion loss: 7 mg/cm.sup.2 or less
.circleincircle., less than 10 mg/cm.sup.2 .largecircle., and 10
mg/cm.sup.2 or more X. *5 .largecircle. means being acceptable with
respect to all the evaluation items (a) to (f).
[0172] A summary of the evaluation test results of resin
compositions and printing plates obtained in Examples 19 to 24 are
listed in Table 5.
[0173] Table 5 shows that satisfactory performance can be obtained
with various reactive emulsifiers, amounts, particle diameters,
etc. without exception.
5 TABLE 5 Example Example Example Example Example Example 19 20 21
22 23 24 (A) Composition of hydrophilic copolymer (pts. wt.) (1)
acrylic acid 2 2 2 2 2 2 (1) methacrylic acid 5 5 5 5 5 5 (2)
butadiene 60 60 60 60 60 60 (3) styrene 10 10 10 10 10 10 (4) butyl
acrylate 23 23 23 23 23 23 Reactive emulsifier *1 (i) (i) (ii)
(iii) (i) (i) Total amt. of reactive emulsifier (pts. wt.) 2 4 4 4
15 4 Nonreactive emulsifier species *B Total amt. of nonreactive
emulsifier (pts. wt.) 0.0 0.0 0.0 0.0 0.0 0.5 t-Dodecylmercaptan
2.0 2.0 2.0 2.0 2.3 2.0 Emulsion polymn. temp. (.degree. C.) 80 80
80 80 80 80 No. av. particle diam. of copolymer (A) (nm) 80 55 52
51 15 58 Toluene gel ratio (%) 87 90 90 90 91 89 Evaluation (a)
compatibility (dispersibility) .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. (b)
developability with aqueous developer .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
.circleincircle. solution *2 (c) image reproducibility
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. (d) water swelling ratio (water
resistance) (%) *3 1.0 1.0 1.0 1.0 1.2 1.2 (e) print wear
characteristics *4 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .largecircle.
(f) plate wiping-off resistance .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. Overall
evaluation *5 .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. *1 Emulsifiers (i) to
(iii) refer to emulsifiers (i) to (iii) specified on pages 20-21 of
this specification, respectively. *B Nonreactive emulsifier: sodium
(dodecyl diphenyl ether) disulfonate. *2 Developing time: 17 min/mm
or less .circleincircle., less than 20 min/mm .largecircle., and 20
min/mm or more X. *3 Water swelling ratio when 1.3% or less was
regarded as being acceptable. *4 Abrasion loss: 7 mg/cm.sup.2 or
less .circleincircle., less than 10 mg/cm.sup.2 .largecircle., and
10 mg/cm.sup.2 or more X. *5 .largecircle. means being acceptable
with respect to all the evaluation items (a) to (f).
Industrial Applicability
[0174] When the photosensitive resin composition for flexographic
printing according to the present invention is employed, the
compatibility (dispersibility) of hydrophilic and hydrophobic
components of the photosensitive resin composition can be enhanced;
and developing time with an aqueous developer solution can be
shortened. Furthermore, there can be obtained the printing plate
characterized in that the resistance to water base ink is high;
that the image reproducibility is excellent; that high print wear
characteristics can be maintained even when a water base ink is
adhered; and that the plate wiping-off resistance in removing the
ink adhered to the printing plate is high.
* * * * *